The present invention relates to a management system according to the preamble of attached claim 1 for managing a telecommunications network. The telecommunications network to be managed may be e.g. a SDH (Synchronous Digital Hierarchy) network, a PDH (Plesiochronous Digital Hierarchy) network, or a combination of such networks.
The basic situation in network management is usually such that an operator managing a telecommunication networks, e.g. a telephone company, has a plurality of customers (i.e. network users) in addition to the physical network. The operator sells the customers various services that utilize the network. (A public network will be used herein as an example; in principle, however, the same description applies to a private operator managing e.g. an organisation network). To meet customers' data transmission requirements in the physical network, the operator utilises a number of facilities or operative processes for the provision of customer services. These operative processes can be divided into groups in accordance with the functions for which they are intended:
Service Provisioning taking care of the performance of customer services, including e.g. invoicing customers for services. PA1 Operation & Maintenance for keeping the network operative to allow the usage of customer services. One of the most important functions in this respect is the supervision and repair of network faults. PA1 Planning & Development, the function of which is to develop network operation so as to better meet customers' needs and to increase the overall profitability of the operator enterprise. PA1 network element management layer, PA1 network management layer, PA1 service management layer, and PA1 business management layer. PA1 OK. There are no problems. PA1 Warning. There are outstanding faults, but these do not affect services. PA1 Degraded. Some or all of the services provided by the object are degraded. PA1 Failed. All the services provided by the object are lost. PA1 Unknown. The fault state of the object is unknown. PA1 Enabled. The object can operate, either completely or in part. PA1 Disabled. The object cannot operate at all.
As appears from the above, network management takes place on several different levels, depending on the extent to which the functions to be performed on a specific level are associated with the overall management of the operator enterprise. The management of a telecommunications network is generally divided into four different levels, which are from bottom to top as follows:
This division is used e.g. in the ITU-T (the former CCITT) recommendation M.3010, which specifies a kind of framework for the management architecture of a telecommunications network. The bottom layer below the above four layers is the equipment itself; these equipments are managed by installation and field engineering tools.
The network element management layer means the management of an individual network element (such as a multiplexer or a cross-connection device) as a separate component without simultaneously paying attention to the condition of the network or other network elements. The majority of so called "network management" systems commercially available today are actually network element management systems within this layer.
The network management layer is concerned with the management of the entire telecommunications network, such as overall management of network connections. One example is the creation of connections and the end-to-end supervision of their condition. This means that e.g. alarms detected on equipment are not just displayed against that equipment, but they are also propagated to show what services (paths and circuits) are affected by the fault, if any. The present invention is positioned in this layer.
As distinct from the above, the service management layer is not concerned with technical network management. It takes care of e.g. customer data, supervision of services provided to customers, invoicing for services, and considering needs for services of different types.
The business management layer is used to monitor and plan the business activities and economy of the entire enterprise, resulting in decisions affecting the lower levels.
At present, network management systems are changing into systems that manage the telecommunications network as a whole, whereas conventional management systems have handled only the remote control of transmission equipment, especially monitoring alarms produced by the equipment. In conventional network management methods, configuration changes, such as creation of new end-to-end connections, have been laborious and time-consuming, as the end result consists of several configuration events the pre-requisite of which is that the maintenance staff of the network first gets an overall view of the situation and then decides on configuration changes required in individual network elements. In new network management systems, on the contrary, an overall view of the network and its condition is produced within the system, and the system itself gives the required configuration commands to each transmission equipment. As a consequence, all configuration changes can be performed significantly more rapidly than previously. Such developments have been accelerated by the freeing of competition in the field of telecommunications.
The above-mentioned recommendation M.3010 specifies the management architecture as shown in FIG. 1. The architecture basically consists of one or more operations systems OS connected to a data communication network DCN communicating with an actual telecommunications network which is to be managed and which includes the network elements NE managed. It is to be noted that the connections of the data communications network and those of the telecommunications network are logically distinct, although they can be implemented physically in one and the same cable. Logically, there are thus two networks: (a) a network providing services to customers, and (b) a network maintaining the service provisioning network. The management of certain transmission equipments (network elements) further requires a separate Mediation Device MD, which mainly acts as a protocol converter between a Q3 interface complying with the recommendations and transmission equipments that do not understand the protocol applied in the interface but use their own proprietary protocol. New SDH equipment, for instance, can be connected directly to the Q3 interface, whereas older PDH equipment requires a Mediation Device.
In practice, a management network for a combined SDH and PDH network may be e.g. such as shown in FIG. 2. Users (network operator staff) sitting at the operation centre use network management work stations WS connected to a separate local area network WSN, which may be e.g. an Ethernet network. The management system is typically distributed in several computers of the local area network, one of the computers being a dedicated application server SRV having a database DB containing information necessary for managing the network. In its practical embodiment, the local area network further comprises e.g. necessary back-up devices (like DAT drives or mirrored disks) and event-logging printers (not shown).
The management system is connected via the above-mentioned Q3 interface e.g. to the SDH network. A variety of alternatives have been defined for the Q3 interface, so that the interface may be e.g. an X.25 type packet switched interface or an Ethernet LAN interface. (The packet switched interface is useful if the operator in charge of the network management also otherwise uses a packet switched network.) In practice, control channels between the SDH network elements 21 are established in the overhead bytes of the STM-N signal (N=1, 4, 16), so that control signals between SDH equipments propagate with the pay-load signal (that is, also in the same physical network). Such control channels established in the overhead bytes are called Embedded Control Channels, and they are formed e.g. in the STM-I frame by the section overhead bytes D1 to D12.
PDH equipments, on the contrary, need manufacturer-specific solutions, wherefore they have to be connected to the management system through a separate mediation device 22.
The management system may also be hierarchical so that different geographical areas have their own smaller management systems that together form an integral management network. For instance, a management system covering one country may be divide geographically into smaller management systems operating in different parts of the country. Each smaller management system takes care of the management of the network portion in the concerned geographical area. In the example of FIG. 2, management systems MS1 and MS2 geographically apart from each other form together a single common management system and management network.
Network management standards are nowadays largely based on so-called object-oriented descriptions, though the standards do not require the use of this technique. Objects are data structures in a network management system, which describe the functions and state of a network component. An object is thus an element having certain attributes ("I am like this") and certain operations ("I can do these things"). (In the object-oriented approach, objects with the same data structure (attributes) and the same behaviour (operations) are grouped into a class. A specific implementation of an operation is called a method and each object is said to be an instance of its class.) A typical object is e.g. a cross-connection device with certain attributes (cross-connections that are active) and certain methods (e.g. make cross-connection and release cross-connection).
In a telecommunications network management system, objects can be physical ones or logical ones. Physical objects are elements that form part of the physical network. Such objects are e.g. the above-mentioned network elements (a network element is any piece of telecommunication equipment that works as a single unit to provide telecommunication functions) or physical connections (such as optical fibres, twisted pair cables, coaxial cables, radio links or satellite links). Logical objects are logical entities that do not form a single piece of the physical network. Such objects are e.g. paths and circuits. (A path is a connection of a fixed bit rate and format between two physical interfaces within the network. A circuit is a connection set up for a customer, between two physical interfaces on the boundary of the network. Thus, a circuit usually comprises several consecutive paths.)
A network object may have a number of different attributes. Some attributes (such as "fault state") are used by several different types of object. In addition, for some types of network object (such as a route), it is convenient to define an attribute which consists of a collection of other attributes. Typical attributes are e.g. "availability status", "fault state" and "operational state". The attributes have different possible values, e.g. fault state can have values:
The "operational state", in turn, can have e.g. two different values:
One of the problems relating to a management system is how to be able to manage a wide diversity of equipments using protocols of different kinds.
First, a network to be managed comprises devices with very different basic functions, such as multiplexers or cross-connection devices. Second, there are older and newer versions of devices effecting the same function, and such versions may be technologically quite different from each other, e.g. PDH and SDH equipment effecting the same function (such as cross-connection). The properties of the same type of equipment (such as cross-connection devices) vary with the manufacturer; the different versions of one and the same device may also differ from each other even though the manufacturer is the same.